Conformational analysis and photolysis of matrix isolated 3-chloropropanoyl chloride monitored by FTIR spectroscopy

Abstract

Fourier transform infrared spectra of 3-chloropropanoyl chloride 1, both as a neat liquid and isolated in an argon matrix at 10 K, have been analyzed. These spectra reveal the existence of three conformers, the SA conformer (ф 1(C3C2ClO) = 0° and ф 2(C1C2C3Cl3) = 180°) being the most stable. The semi-empirical PM3 and ab initio 6-31G∗ methods were used to evaluate the relative stability of these conformers, and to calculate the infrared spectra. Irradiation of 3-chloropropanoyl chloride, at λ > 230 nm, yields 3-chloro-1,2-propenone 2 and acryloyl chloride 3 as primary photoproducts. Photolysis of these compounds induces the formation of CO, HCl, vinyl chloride and ethyne as final products. The shifts of the ν HCl stretching mode, below the frequency of monomeric HCl in argon matrix, are indicative of the formation of HCl : CO and HCl : ethyne complexes. The identification of the reaction products is performed by comparison of experimental FTIR spectra and literature data.